The lights across Britain will not go out this winter "under any scenario whatsoever", Trade and Industry Secretary Alan Johnson has insisted.
Gas problems also affect electrical supplies
He gave the assurance despite experts predicting the country is about to face the coldest winter in a decade.
It also comes amid fears about rising gas prices and energy supplies.
Energy Minister Malcolm Wicks later told MPs the National Grid was "awash with gas". He accused the Conservatives of trying to "talk up a crisis".
'Government on skids'
The subject was also raised at prime minister's questions when Tony Blair admitted the country faced "difficulties with gas prices" due to the impending cold winter.
But he said that while the energy industry was doing its "level best" to meet demand, it was not a problem that "lies within the remit of government itself to resolve".
However, Tory leader Michael Howard said the failure to guarantee supplies suggested that the government was on the "skids" and unable to cope with the challenges it faces.
Immediately after prime minister's questions energy minister Mr Wicks, was forced to answer an urgent Commons question on energy supplies.
He said some heavy business users of gas, particularly chemical companies, were suffering from high gas prices.
It was up to individual companies to decide when and how they bought their energy supplies, he said.
Conservative shadow energy minister Bernard Jenkin said industry would be "astonished to hear you saying that we are awash with gas when they are facing the prospect of interruptions to their gas supplies".
And Norman Lamb, the Liberal Democrat trade and industry spokesman, told BBC News he was concerned that "massive increases" in gas prices could hit the poorest people.
Mr Wicks later wrote to the Tories detailing what he said were many months of "unprecedented" contacts with heavy industry and energy companies about price and supply issues.
Mr Johnson told the Commons environmental audit committee that intensive users of energy "may see an effect" if the cold snap was worse than predicted this year.
But he added: "Those that predicted that the lights might go off this winter in the media and had front page stories saying 'blackout' unnecessarily worried some very vulnerable and elderly people.
"That's not going to happen under any scenario whatsoever."
The government is about to announce a review of energy policy, including nuclear power.
At prime minister's questions, ex-environment minister Michael Meacher demanded to know why Mr Blair had said "the government has got to take on nuclear power" when it was more expensive than coal and gas.
Mr Blair said a proper debate was needed because by 2020 the amount of energy from nuclear power would fall from just over 20% to 4%, and trying to meet that shortfall through renewable sources was "going to be difficult".
Mr Johnson said the government was "genuinely open-minded" about the use of nuclear option, which would be considered, along with renewable alternatives like tidal power.
There was "no expectation of taxpayers' money being thrown into" a new nuclear building programme, he said - it would be down to the private sector to fund it.
"I think there's a fair argument there that they are actually waiting to see what the political temperature is and what government's approach here is going to be before they make hard and fast plans," he said.
Any decision to go forward with the nuclear option would be based on security of supply, affordability and carbon emissions, he added.